gpu/drm/hisilicon: Convert drm_atomic_helper_suspend/resume()

convert drm_atomic_helper_suspend/resume() to use
drm_mode_config_helper_suspend/resume().

Fixed one sparse warning by making hibmc_drm_interrupt
static.

Signed-off-by: Ajit Negi <ajitn.linux@gmail.com>
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Reviewed-by: Xinliang Liu <z.liuxinliang@hisilicon.com>
Signed-off-by: Xinliang Liu <z.liuxinliang@hisilicon.com>